A Growing Degree Day Model to Schedule Trinexapac‐ethyl Applications on Agrostis stolonifera Golf Putting Greens

Abstract

Trinexapac-ethyl (TE) is a widely used growth regulator in the turfgrass industry. Poor summer efficacy has been related to more rapid metabolism in the plant. The purpose of this study was to determine if a growing degree day (GDD) model could be used to identify the optimum TE reapplication interval for putting greens. This objective was accomplished through model development and validation. Model development was conducted on a creeping bentgrass {Agrostis stolonifera L.) golf putting green in Madison, Wl, during 2008. The treatments consisted of five TE reapplication intervals (100, 200, 400, 800 GDD, and 4 wk) and a control. Growing degree days were calculated in degrees G with a base temperature of 0°G. Trinexapac-ethyl was applied at the rate of 0.05 kg a.i. ha"^ Clippings were collected daily. The 100-and 200-GDD reapplication intervals provided consistent 20 and 12% yield suppression, respectively. Other reapplication intervals had alternating periods of yield reduction followed by yield enhancement. Model validation occurred on a different creeping bentgrass green in 2009 and 2010. The experiment was a 3 X 2 factorial GRD with three TE rates (0.00, 0.05, and 0.10 kg a.i. ha"^) and two reapplication frequencies (200 GDD and 4 wk). The 200-GDD interval consistently suppressed clipping yield. Application rate had no effect on the duration of suppression. Reapplying TE every 200 GDD provides more consistent growth regulation than a calendar-based application schedule.

Growing Degree Day Models for Plant Growth Regulator Applications on Ultradwarf Hybrid Bermudagrass Putting Greens

“…Knowledge of the cumulative GDD to reach peak suppression was important to determine application intervals of PGRs that maximize growth suppression and minimize rebound growth (Kreuser and Soldat, 2011). Kreuser and Soldat (2011) suggested that PGRs are to be reapplied at 1.3× the GDD value at peak suppression to minimize rebound growth and maximize PGR benefits.…”

“…The methods for development of a GDD model for TE applications on bermudagrass putting greens were similar to those outlined by Kreuser and Soldat (2011) and Kreuser et al (2017). Experiments were conducted June to October 2017 on three ultradwarf hybrid bermudagrass cultivars at three separate locations in the southeastern Untied States: MiniVerde at the East Tennessee Research and Education Center in Knoxville, TN; Champion at the Hope Valley Country Club in Durham, NC; and TifEagle at the R.R.…”

“…Air temperatures have been reliable for determining optimal TE application intervals on creeping bentgrass putting greens using a cumulative growing degree day (GDD) model (Kreuser and Soldat, 2011; Kreuser et al, 2017). The GDD model subtracted a base temperature from the daily mean air temperature and then added the remainder to the previous day's temperature.…”

“…The cumulative GDD was then correlated to creeping bentgrass clipping yield after a TE application. Kreuser and Soldat (2011) stated that TE applications every 200 GDD (base 0°C) sustained season‐long yield suppression and consistently provided the greatest turfgrass quality on creeping bentgrass greens ( Agrostis stolonifera L.). Development of a GDD model to determine PGR application frequencies on ultradwarf hybrid bermudagrass putting greens would be beneficial to achieve season‐long yield suppression in an array of environmental conditions.…”

A Split Application Approach to Nitrogen and Growth Regulator Management for Perennial Ryegrass Seed Production

“…A split application of a GRP generally results in a positive TSW and SV response to N rate while plots treated with a single application of a GRP demonstrated a negative TSW and SV response to N rate (Table 7). Split applications of a GRP may be more effective at providing season long vegetative growth suppression than single applications at higher rates (Kreuser and Soldat, 2011), which could potentially result in higher quality seed in a seed production field. Previous studies have shown that GA inhibitors can increase WSC within grass plants following application so the positive TSW and SV response to N rate could be due to a combination of increased WSC production and WSC transport during seed fill as a result of greater efficacy of the split GRP application (Han et al, 2004, Rolston et al, 2010b.…”